1. Field of the Invention
The present invention relates to a display apparatus such as an active matrix type liquid crystal display apparatus and a driving circuit for driving the display apparatus. In particular, the present invention relates to a display apparatus for AC driving signal lines and pixel electrodes in a display region and a driving circuit thereof.
2. Description of the Related Art
Liquid crystal display apparatuses have been widely used as display devices for TV sets and graphics display devices due to their advantageous features of thin structure and low power consumption. Among them, since an active matrix type liquid crystal display apparatus using thin film transistors (referred to as TFTs) as switching devices have high speed response characteristic and a high precision characteristic, this apparatus is becoming attractive for its high picture quality, large size, and color pictures.
When a DC voltage is supplied to a liquid crystal pixel of a liquid crystal display apparatus, the liquid crystal material deteriorates and the liquid crystal pixel bakes. In addition, the display quality deteriorates due to an adverse effect of a capacitance caused between signal lines and pixel electrodes. Thus, to solve these problems, it is necessary to supply a positive phase picture signal and a negative phase picture signal that alternately vary to each liquid crystal pixel.
However, in the conventional liquid crystal display apparatus, since the positive phase picture signal and the negative phase picture signal are supplied with the same line, when the positive phase picture signal is switched to the negative phase picture signal, the electric charges in the line should be discharged until the negative phase picture signal is obtained. Thus, the power consumption of the external picture signal supplying circuit of the AC driving circuit is larger than that of the non-AC driving circuit.
To solve this problem, a method for supplying a positive phase picture signal from one end of a signal line and a negative phase picture signal from the other end of the signal line has been proposed in Japanese Patent Laid-Open Publication No. 3-51887.
However, in this method, since buffers are disposed at input terminals of a picture signal at both ends of a signal line, only one of the positive phase picture signal and the negative phase picture signal is supplied to one signal line. Thus, when the performance of the switching devices is low (namely, the ON resistance is high or the write time is short), the same phase voltage should be supplied to both ends of one signal line. In this case, this method cannot be used.